When fluids are present in microliter quantities, it is generally desirable to mix them in channels or passages having micrometer-sized dimensions so that the fluids are not wasted. However, fluids generally behave differently when they have to pass through channels and passages having micrometer-sized dimensions. For example, water flowing through a channel having a diameter equal to the width of a human hair behaves like honey. Even under pressure, the water travels less than one centimeter per second. Mixing of two different fluids in channels or passages that have micrometer-sized dimensions is therefore difficult because at such dimensions, the fluid's ability to flow in a turbulent manner is minimized. In channels or passages having micrometer-sized dimensions, static diffusion between two different fluids takes a prohibitively long time.
It is therefore desirable to have a mixer that can facilitate the mixing of a plurality of different fluids when the fluids are present in quantities on the order of microliters.